Abstract
Considerable progress has been achieved in developing strategies for the eradication of P. ramorum and P. kernoviae in both nurseries and the wider environment. These strategies have largely focussed on the removal of infected host material and contaminated leaf/plant debris. Monitoring carried out over the last two years in managed gardens has demonstrated that when eradication action has been taken promptly, and vigilance maintained on treating/removing re-growth of the host, it has been possible to prevent further infection of host plants. However, analysis has also shown that the pathogens can persist in the environment, particularly in soil, pathways and watercourses, and evidence is starting to accumulate that residual root and stump material (remaining in the ground following eradication) may also harbour the pathogen. On affected nurseries there has been similar success with the majority of nurseries being able to eliminate the pathogen from the site. However, there are still a significant number of nurseries on which P. ramorum can still be detected or where recurrent outbreaks continue to occur. Sources of inoculum for these outbreaks remain unclear. The proposed project aims to investigate and identify sources of residual inoculum at key nurseries where recurrent outbreaks have occurred and to monitor ongoing contamination at selected garden/woodland outbreak sites where eradication action has been taken. Levels of contamination will be investigated using newly developed quantitative methodologies for detection of P. ramorum and P. kernoviae. This will allow investigation of the scale of contamination in each situation and give a more accurate measure of changes in inoculum levels over time. Following quantification of base-line inoculum levels, treatments and strategies to achieve effective decontamination of the affected substrates will be evaluated. A further aspect of the project will be to use quantitative methods to measure inoculum levels in the air and during rainfall at a heavily infected site and to use new spatial techniques to measure the development of disease on rhododendron plants infected with either P. ramorum or P. kernoviae. Data on inoculum and disease levels will be analysed in relation to seasonal and local factors to identify key drivers which affect the buildup of inoculum and the risks of further plant infections occurring.
United Kingdom